Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$184.38	11.552%	$205.6796	$205.68	$205.70	$205.70
Purchase #2	$67.32	6.397%	$71.6265	$71.63	$71.65	$71.60
Purchase #3	$30.90	3.180%	$31.8826	$31.88	$31.90	$31.90
Purchase #4	$222.44	4.470%	$232.3831	$232.38	$232.40	$232.40
Purchase #5	$59.69	12.871%	$67.3727	$67.37	$67.35	$67.40
Purchase #6	$114.80	9.812%	$126.0642	$126.06	$126.05	$126.10
Purchase #7	$108.33	7.314%	$116.2533	$116.25	$116.25	$116.30
7 purchase totals =	$787.86		$851.2620	$851.25	$851.30	$851.40